Electronic telephone exchange



E. M. DELORAINE ET AL ELECTRONIC TELEPHONE EXCHANGE May 8, 1951 4 Sheets-Sheet 1 Original Filed March 14, 1946 (rum INVENTOR. EDMOND M. DELORAINE BDYAV D H. RANSOM ATTORNEY E. M. DELORAINE ET AL Re. 23, 3

ELECTRONIC TELEPHONE EXCHANGE May 8, 1951 2a la 40 i j LOCKIN PHASE o5zc|g.a' r 0R WHHI-LT 35 1 T0 50 KC l LOCKIN GATE 36 -1- 134 .L- CLIPPER mrranzumt 7 ms CIRCUI J DELAY 25 I GAIN TUBE RELEASE CONTROL LINE FINDER TALKING CIRCUIT ,us R R LOW LOW PASS PASS AMPLIFIER FILTER FILTER DAV! D H. RANSOM BY May 8, 1951 E. M. DELORAINE ET AL 23,363

ELECTRONIC TELEPHONE EXCHANGE Origipal iiled March 14, 1946 4 Sheets-Sheet 3 [I05 2 12 1 fol a L EL Ji s T L T T wvwo I" HQQQQ PULSE Y a "A'Tfi 74 5+ 4 =F= .7 L l J L v H T a m- T -\NH x1: l

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1 10 T M T 1o 1 m [I r L 7 T wi i av I PNE stLzc'rmc mulPuzu-r' A TTORA/Ey 4 Sheets-Sheet 4 E. M. DELORAINE ETAL ELECTRONIC TELEPHONE EXCHANGE May 8, 1951 Original Filed March 14, 1946 INI'ENTOR. DELORAI N E RANSOM A TORN EDMOND M. DAVID H. BY

Reissued May 8, 1951 ELECTRONIC TELEPHONE EXCHANGE.

Edmond M. Deloraine, Rivervale, and David H. Ransom, Paterson, N. J., assignors to Federal Telecommunication Laboratories,

Inc., New

I York, N. Y., a corporation of Delaware Original No. 2,492,136, dated December 27, 1949,

Serial No. 654,326, March 14, 1946. Application for reissue December 23, 1950, Serial No.

15 Claims.

This invention relates to new and useful improvements in communication systems and more particularly in telephone systems of the type disclosed in the copending application of E. M. Deloraine, Serial No. 628,613, filed November 14, 1945, now forfeited.

The object of the present invention is to provide [a ringing and] an improved two-way talking arrangement for an all-electronic telephone exchange system, i. e. one in which no electromagnetic equipmemt is used for establishing connections.

With this object in view we provide an electronic repeater through which two-way signalling may be accomplished [including the sending of a ringing signal] from the central exchange to the called line.

In accordance with the embodiment here disclosed two electronic means such as cathode ray tubes are provided in common for the lines. Signals such as dial and speech signals may be sent from both the calling and the called lines through one of the cathode ray tubes, and the signals such as speech and ringing signals may be sent to the line through the other cathode ray tube.

These and other features of the invention will more readily appear from the appended claims and the following detailed description of a preferred embodiment, of which as much as is necessary for an understanding of the invention is illustrated in Figs. 1 to 4 of the drawings. In reading the drawings, Fig. 2 should be placed below Fig. 1, Fig. 3 to the right of Fig. 2 and Fig. 4 to the right of Fig. 1, Figs. 1 and 4 are being kept horizontal and Figs. 2 and 3 in vertical.

Fig. 1 shows the substation equipment of one line and the two electronic means and associated equipment common to the lines, the upper part of Fig. 2 the line finder, and the lower part the talking circuit and signal repeater equipment,

Fig. 3 the registering and line selecting equip-' ment and Fig. 4 the dial pulse and ringing equipment.

Each subscribers line is provided with a subset I of any conventional type, a calling dial 2 by means of which, in the embodiment here disclosed, one to twenty impulses may be sent depending on the designation of the called line, a hybrid coil 3, and a balancing network Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

4. The interconnection of calling and called lines is effected by means of a pair of cathode ray tubes of which 5 is employed for receiving signals (including speech) from the line and 5 for transmitting signals (including speech, ringing, and the like) to the lines. The lines terminate on electrodes forming dynodes in the cathode ray tubes, one winding of the hybrid coil 3 being connected to terminal electrodes of tube 5 and another winding to the electrode terminals of tube 6. Each tube is equipped with the customary gun structure and deflecting means for the purpose of sweeping cyclically and in succession the line terminal electrodes provided therein. The beams of these tubes may, for instance, rotate (assuming that the line terminals are arranged in a circle) under the control of a master oscillator 1 operating at 200 kc. and connected in multiple with the deflecting plates of the two tubes through a 10 kc. frequency divider 8 and a phaser 9, insuring a repetition rate of 10 kc. per second of the scanning beam.

When the subscriber at station I initiates a call the operation of the switch hook (not shown) at the subset l places a negative potential on the anode l2 through the dynode of the calling line in the receiving tube 5 over a circuit extending from the negative pole of grounded battery [0 over a retardation coil II, a loop including the secondary of the hybridcoil 3, the subset I, and dial 2. This causes a flow of electrons from the terminating electrode in the tube to anode I2 each time the scanning beam sweeps over the dynode of this line. The resulting negative pulse I3 is fed to the grid of a cathode follower and inverter tube [4. The negative pulses IS in the cathode output of tube M are applied to the grid of a clipper amplifier tube l6. Tube Iii is normally biased by resistor ll to draw current, and the signal amplitude is so adjusted that each negative pulse l5 will drive the tube I5 beyond cut-off whereupon the tube will clip variations caused in the signal by dial pulses or transmitter modulation.

The positive pulse [8 appearing in the plate output of tube i6 is fed to the grid of cathode follower l9 and through the cathode thereof to conductor 20 which is multiplied to the grids of all line finder gate tubes 2|.

The line finder gate tubes 2| are normally biased through battery 22 far enough beyond cut-off so that the incoming positive signal |8 will not affect their plate output.

A lock-in oscillator 23 in the line finder operates at a frequency slightly below the rate of scanning in the tubes 5 and 6 ('200 kc.), and divides this output to a frequency of approximately 50 kc. The sine wave output of oscillator 23 passes through a clipping amplifier and differentiating circuit 24 in the form of pulses 25 to a multivibrator 26 arranged to synchronize at approximately kc. The output-pulses 21 of a multivibrator 26 aredifferentiated in a network 28 and the resulting pulses 29 are ap-: plied to the control grid of a clipper gate tube 3|]. The constant and the bias of this gate tube are adjusted so as to produce by the leading edge of the differentiated pulses 29 in the plate circuit thereof a short square pulse 3| of approximately 5 microseconds duration. The trailing edge'of the pulses '29 is suppressed in tube'30.

The negative pulse 3| is passed through a cath ode follower 32 as pulse 33 which is applied to the cathode of the line finder gate 2|. The amplitude of pulse 33 is adjusted by delay gain tube 34 so that normally the line finder gate tube 2| remains cut off. This gate has a positive pulse I8 applied to its grid and a negative pulse 33 to its cathode, neither of which will drive it beyond cut-01f to produce conduction. Since the lock-in oscillator 23 has a frequency which is slightly less than that of the master oscillator 1, the pulse 33 will drift with respect to the pulse l8 until the two will occur simultaneously whereupon the bias of the line finder gate tube is overcome. When this happens then a negative signal 34 appearing in the plate is passed through a rectifier 35 and an integrating net 36 to the grids of the delayed gain tube 34 and of the gate control tube 31. The latter will be driven to cut off after a few pulses 34 have reached it, permitting the lockin gate tube 38 to pass a signal received from the master oscillator 1 over a wire 39. The output of the lock-ingate tube 38 will synchronize oscillator 23 with oscillator 1. A phase corrector 43 inserted between the plate of grid 38 and the oscillator 23 insures accurate adjustment.

The portion of the rectified output of rectifier 35 which was fed to the grid of the delayed gain tube 34 will drive the latter beyond cut-off after a few pulses. The plate of tube 34 and the screen grid of clipper gate 30 are connected to a common resistor 4|. The screen voltage of gate 30 will, therefore, rise and will cause an increase in the amplitude of pulse 3| and, therefore, of pulse 33 which is the pedestal pulse applied to the cathode of line finder gate 2|. This will cause the grid of tube 2| to be driven positive by the pulse I8 and clipping by grid current will occur. However, the amplitude of the incoming pulse |8 will be insuflicient to affect the line finder gate tube of any other link.

The output pulses 34 of the line finder gate are supplied also over conductor 42 to the grid of an input gate control tube 43. The plate of tube 43 is connected in multiple to the suppressor grids of two tubes; one of these is an input gate tube 44 whose pair is 45, and the other is an output gate tube 46 whose pair is 41. The two pairs of input and output gate tubes 44 and 46 are normally biased to cut-off on the suppressor grid by the voltage drop in plate resistor 43 of the input gate control tube 43. Similarly, the input and.

output gate tubes 45 and. 41 are normally biased 4 to cut-01f on their suppressor grids by the voltage drop in plate resistor 49 of output gate control tube 50.

The negative pulse 34' coming from the line finder gate drives the grid of control tube 43 beyond cut-01f which will reduce the voltage drop across its plate resistor 48 to zero. This will raise the bias on the suppressor grids of gates 44 and 43, permitting the passage of signals which may appear on the control grids of these gate tubes.

It is assumed that speech and dial pulses will modulate the line signal at, say, 25%. The clipping action of tube "5 Will cut-off the modulated portion so that the pulse |8 which is applied to theline finder gate will be uniform. However, a

clipper tube 5| is so biased that only the modulated portion of a positive pulse 52 applied thereto by the inverter M will appear in the grid of a cathode follower 53. Cathode output 54 of tube 53 is applied over conductor 55 to the control grids of the input gate tubes 44 and 45 in all links but will'affect only the pair whose control-tube 43 is opera-ted by the pulses 34.

The pulses produced by the dial 2 of the calling line will thus be transmitted as pulses 54 under control of gate control 43, and through the plate of input gate 44 over conductor 56 and a pulse stretcher and integrating network 51 to'the grid of an amplifier 58 in the form of positive pulses 59. These low frequency dial pulses 59 are amplified by tube 58 and shaped in a clipper tube 3!! to form negative square wave pulses 6|. The pulses 6| are differentiated in a network 82 into pulses 63 which are applied to the control grid of dial gate tube 64. Thelatter is biased so that the leading edge of the differentiated pulse 63 is suppressed and the trailing edge thereof is passed as a negative pulse 65 over conductor '53 to the register circuits.

The pulses 59 are passed in parallel over a pulse stretcher and integrating net H2, and the leading edge of the first pulse of a series flips conduction from tube 61 to tube 68 in the dial gate control. The circuit constants are such as to maintain this condition until the end of the dial pulses when tube 61 again becomes conducting and sends a negative pulse to the dial gate control 59, 10 and to the ringing gate control I02, I03. The output of tube 13 is applied over conductor 1| to the suppressor grid of dial gate 64, biasing the latter to out off. This will lock out the register so as to protect it against transients.

The register circuits are also conventional Eccles-Jordan trigger circuits connected to form a strip count. Initially, the right-hand tube 13 of the No. 0 register and the left-hand tube 14 in the No. I register and of all subsequent registers are conducting. The first negative pulses 65 on conductor 66 will transfer conduction in the- No. 0 register from tube 13 to tube 12. The negative pulse appearing in'the plate of tube 12 will be applied to the grid of tube 14 in the No. 1 register so as to transfer conduction to tube 15 of the latter.

The next pulse 65 will produce the same operations as above explained, except that now registers Nos. 1 and 2 will be involved. After a series of pulses 65, representing the dial pulses at the calling station, have been received, the righthand tube of one of the registers will be in conducting condition. A potential will be applied to the supressor grid of the corresponding time channel gate tube 18, 19 or associated with this register, permitting the passing of a signal from the control grid of the time channel gate.

The line selecting circuit proceeds now to count the digit pulses as set in the register, synchronizing on each count with a zero pulse 8| applied to the No. counter over a conductor 82 from a zero pulse generator 83 which is driven by the 10 kc. frequency divider 8.

Normally, the left-hand tubes 84, 86, 88, etc. 90 of the counters are conducting. The synchronizing pulse 8| flips conduction in the No. 0 counter from tube 84 to tube 85. Negative pulses 92 which are derived from master oscillator 1 over conductors 39 and 93 and a pulse-shaping amplifier 94 at microsecond intervals are applied over a common conductor 95 to the grids of all the right-hand counter tubes 85, 81, 89 and 9|.

The negative pulse 92 following the synchronizing pulse BI will transfer conduction in the No. 0 counter from tube 85 to tube 84. The negative pulse appearing in the plate circuit of 84 is applied to the grid of the left-hand tube 86 in the No. 1 counter and will flip conduction to 81.

Each successive pulse 92 will flip a counter so as to make its right-hand tube conducting until all the counters are operated, whereupon the final pulse restores the circuit to normal. Depending on the register which is operated, one of the time channel gate tubes 18, 19, etc. 80 will permit the passage of a signal which is applied to its control grid by the right-hand tube of the operated counter, and this pulse 96 is transmitted over conductor 91 to the control grid of the output gate control tube 50. If, for example, the No. 1 register is conducting on its right-hand tube 15, then the positive bias on it is transferred over conductor 98 to the suppressor grid of time channel gate tube 18, so that when the No. 1 counter flips conduction to its right-hand tube 81 a negative signal 96 will be generated on the plate of tube 18.

The negative pulse 86 is applied over a conductor 99 and a busy pulse-shaping amplifier I00 to the grid of a busy gate tube IOI whose output added to the pulse I8 appearing in conductor 20 when the beam of 5 sweeps the called line will prevent the operation of a line finder gate tube like 2| when the called subscriber answers.

At the end of a series of dial pulses a negative pulse in the output of dial gate control tube 61 will flip conduction from a tube I02 to a tube I03 in the ringing gate control forming part of the ringing circuit. This will permit a ringing gate tube I04 to send a ringing signal over conductor I05 to the control grid of the output gate tube 41. Whenever the beam of the sending tube 6 sweeps over the dynode in which the called line terminates, ringing signal is applied through the following circuit: From a ringing oscillator I06 to the suppressor grid of ringing gate I04 which has been made operative by the potential applied to its control grid by the ringing gate control, the plate of tube I04, conductor I05, the control grid of output gate tube 41, the plate of tube 41, amplifier I01, the control grid of a pentode I08 whose suppressor grid is controlled over conductor I09 by the dial gate control 69, 10, the plate of tube I08, conductor I I0 and the control grid II I of the sending tube 6. The grid I I I will so control the beam when it impinges on the dynodes of the called line as to cause the operation of a ringer at the called station.

When the beam of tube 5 next engages the terminals of the called party who has answered, the positive signal I8 on the cathode of triode I9 will be applied over conductor I I3 to the control grid of trip ringing tube II4. This tube is now open by virtue of a positive pulse applied to its suppressor grid by triode I I5 which, in turn, is made at this instant conductive by pulse 96 applied to it by the corresponding time channel gate over conductor 91.

Negative pulses II6 produced in the plate of H4 will flip conduction from I03 to I02 in the ringing gate control whereupon ringing will stop.

The circuit is now ready to pass speech signals. Speech signals produced in the calling line will be sent when the dynode of this line is swept by the beam of receiver tube 5 over the anode I2, the cathode follower I4 to the clipper tube 5|, and thence to the cathode follower 53 and over conductor 55 to the control grid of the input gate tube 44. From the plate of input gate tube 44, the signal goes through a low pass filter II1 where it is transformed from a series of pulses to the original speech frequency signal and applied to the control grid of the output gate 41. From the plate of the output gate the signal passes through the amplifier I01, the tube I08 and conductor IIO to the control grid I I I of the sending distributor 6, and through the appropriate dynode thereof to the called line.

The path of the speech signals from the called line to the calling line Will be the same as above described but it will occur when the receiving distributor 5 sweeps over the dynode of the called line and the distributor 6 sweeps over the dynode of the calling line. Furthermore, the pulses 54 applied over conductor 55 will not affect the input gate 44 but the input gate 45 through whose plate it will be conveyed via another low pass filter I I8 to the control grid of the output gate tube 46, the output circuit of which is in multiple with the output circuit of the gate 41.

It will be seen, therefore, that the timing of the two functions is reversed, the input gate control tube 43 operating input gate 44 and output gate 46, and the output gate control tube 50 controlling the input gate tube 45 and the output gate tube 41.

At the termination of a call, when the calling subscriber hangs up, all circuits are released under the control of the delayed gain tube 34. The register circuit and the dial gates which are locked in are released by the release tube H9, I20 and I2I. When the call is initiated the delay gain tube 34 is driven to cut off, reducing the potential on the grid of tube I20 which is connected with the cathode of the delay gain tube 34 over conductor I22. This causes the obvious flip-flop circuit to transfer conduction to tube H9 which sends a negative pulse through a difierentiating network to the grid of tube I2I. The latter is biased beyond cut-off and the pulse has no effect. When, however, the line finder 2| releases, then I I9 again becomes conductive and applies a positive pulse to the grid of I2 I. A negative pulse I23 will then be applied to the conductor I24 which will restore all the registers and the dial gate control tubes to normal.

What we claim is:

1. In a communication system, a plurality of lines, two electronic means common to said lines, each having a plurality of electrodes in which the lines terminate and means for cyclically sweeping the electrodes in each electronic means with an electron beam, a control grid for the beam of the first of said means, a signal repeater having an output connected with said control grid, and timing means for applying to the repeater 16 signals originating on calling and called lines 7 when the beam of the second. of: said electronic means sweeps' over their terminals.

2-. :The system according to. claim Land in which each electronic means-comprises a cathode ray tube.

3. The system accordingto. claim 1, in which the signal repeater comprises a dischargetube having input and outputcircuits, means for effectively associating the input circuit with the electrodes of the calling and called lines when they are swept by the beam in the second electronic means, and means for effectively associatingthe-output circuit with the control grid when the beam of the first electronic means sweeps the electrodes of the calling-and called lines.

1 4. The. system according to claim 1, a pluralityof signal repeaters,- means operative upon the initiation of a call for taking into use one of said repeaters, and means for releasing the repeater taken into use upon the termination of the call.

5. The system'accordingto claim 1, line selecting means common to said lines, means for each line to control the selecting means to select the called line, and means for-operatively associating said selecting means with the calling line.

6. The system according to claim 1, a plurality of line selecting means common to said lines, means associated with the second electronic means for controlling the selecting means to select the called line, and means for operatively associating one of the selecting means with the second electronic means upon the initiation of a call.

[7; The system according to claim 1, signalling means common to said lines, line selecting means common to said lines, means associated with the calling line to operate the selecting means to select the called line, and'means operative thereupon for associating said signalling means with said repeat-er 8. The system according to claim 1, and a hybrid coil for each line having a winding connected with an electrode of the second electronic means.

9. The system according to claim 1, and a balancing network for each line.

[10. In a communication system, a plurality of lines, electronic means common to said. lines and having a plurality of electrodes .in which the lines terminate and means for cyclically sweeping the electrodes with an electron beam, a control grid for the beam, a source of signals common to said lines, a signal repeater having an output connected with said control grid, timing means for applying to the repeater signals originating on calling and called lines when the beam of said electronic means sweeps over their terminals, and means controlled by said timing means for ap-: plying signals from said source to the repeater when the beam sweeps over the terminal of the called line] [11.The system according to claim 10, and means for disabling the last-mentioned means controlled over the called line] [12. The system according to claimlO, and in which said source comprises an oscillator, a con-v nection for actuating said repeater by said oscillator, means controlled by the timing means for establishing said connection and means controlled by the called line for disestablishing said connection] 13. In a telephone system, a plurality of lines, two cathode ray tubes common to said lines, each having a plurality .of electrodes. in which thelines terminateand means for cyclically sweeping with an electronbeam the electrodes, a control, grid for the beam of thefirst tube, a signal-repeatercomprising twoinputand two. output; gate .tubes, each of said gate tubes. having acathode, an anode, a control and a suppressor grid,,means including the. second. cathode ray tube for applying-signals, originatingon the calling and called lines to the control grids of the input, gates, connections including low-passfilters from the anodes of the input gates to the control grids. of the output gates, aconnection for'applying apotential to the suppressor grids of one input. and-one output gate controlled by the .calling and called lines when their terminals are swept by the beam of the second cathode ray tube, a connection from the anodes of the output gates to the control grid of the first cathode ray tube, a connection for applying a potentialto the suppressor grids. of the other input and output gates when the. beam of the second cathoderay tube sweeps over the terminals of the. calledline, a pentode in theconnection leading to the control grid and. having its anode .connectedtothe latter and its control grid to. theanodes of theoutput gates, and means controlled by signalsover the calling and called. lines for applying potentials. to the suppressor grid of said pentode.

. 14;. In a communication system, a plurality of lines, two. electronic: means each haying means for moving a beam of electrons and a. plurality of electrodes in which saidlines terminate, means for operating .said electronic. means continuously and cyclically tov sweep said electrodes with their beams, a. plurality of signal input. and signal output tubes provided in pairs, means operative. .upon hehill tiation. of a. call on a line for selecting an input and output, tube, input, .output and control circuits for thesfilected tubes, means for operating the control circuits to render the selected pair of tubes effective when the beams sweep the electrodes in which the calling andcalled lines terminate and ineffective atall other times, a connection from the output of the input tube to the np o e outpu tube. means .iorv assocating the in u Of t input tube with the electrodes in one electronic means in which the calling and called in s ermina ewhen they are swept. by the beam, a contrcl rid for the other electronic means, and means for connecting the output of the output tube'with said control grid when the electrodes of the calling and called lines, areswept b h eam.

15. The system according to claim 14, and in which e e r ni means. c mprises a cathode ray tube.

The stem ac rdin to claim andin which the input and output tubes have cathodes, anodes, control grids, and suppressor grids.

17. The system according to claim 14, and in which the input and output tubes are pentodes.

18. The system according to claim 14, in which the means for selectin the pair of tubes com.- prises a normally inactive :linefinder gate tube, means for actuating said line finder gate tube upon the initiation of a call, and means for operating the lastrmentioned tube to convey signals from thetelectrodes of the calling and called lines in saidone electronic means to the signal input tube whenever the electron beam sweeps over the terminating electrodes thereof.

. 19. In a te ephone system, a plurality of lines, a sending and areceiving cathode ray tube common to said lines, each tubehaving a plurality of 9 10 electrodes in which the lines terminate, and REFERENCES CITED means for cyclically and successively Sweeping The following references are of record in the with an electron beam the electrodes a control i f grid for the sending tube, a signal repeater having file 0 thls patent or the ongmal patent an output connected with said control grid and 5 UNITED STATES PATENTS timing means for applying to the repeater speech Number Name Date signals originating on calling and called lines 2,185,693 Merta Jan. 2, 1940 when the beam of the receiving tube sweeps over 2,2 3 3 9 skin o 18, 1941 their terminals. 2,265,216 Wolf Dec. 9, 1941 p 10 2,379,221 Espenscheld June 26, 1945 EDMOND DE-DORAINE- 2,379,715 Hubbard July 3, 1945 DAVID RANSOM- 2,387,018 Hartley Oct. 16, 1945 

